Re: [PATCH net] tipc: fix NULL deref in tipc_named_node_up() on empty publication list

[Weiming Shi]

Tung Quang Nguyen <tung.quang.nguyen@xxxxxxxx> 于2026年7月6日周一 17:21写道：
>
> >Subject: [PATCH net] tipc: fix NULL deref in tipc_named_node_up() on empty
> >publication list
> >
> >named_distribute() builds the bulk messages for @pls into @list and then
> >dereferences the tail skb:
> >
> >       hdr = buf_msg(skb_peek_tail(list));
> >       msg_set_last_bulk(hdr);
> >
> >If @pls is empty no skb is enqueued, skb_peek_tail() returns NULL, and
> >msg_set_last_bulk() writes through buf_msg(NULL).
> >
> >tipc_named_node_up() passes &nt->cluster_scope. With a node-id
> >configuration the TIPC_NODE_STATE name is published by tipc_net_finalize()
> >from a work item, which sets the node address before publishing the name.
> >The node accepts links once the address is set, so a link that comes up before
> >the publish runs named_distribute() on an empty cluster_scope:
> >
> > KASAN: null-ptr-deref in range [0x00000000000000d8-0x00000000000000df]
> > RIP: 0010:tipc_named_node_up (net/tipc/name_distr.c:196)
> >  tipc_named_node_up (net/tipc/name_distr.c:196 net/tipc/name_distr.c:221)
> >  tipc_node_write_unlock (net/tipc/node.c:428)
> >  tipc_rcv (net/tipc/node.c:2185)
> >  tipc_udp_recv (net/tipc/udp_media.c:392)  Kernel panic - not syncing: Fatal
> >exception in interrupt
> >
> >TIPC genl ops use GENL_UNS_ADMIN_PERM, so an unprivileged user can reach
> >this from a user+net namespace.
> >
> >Return early from named_distribute() when the list is empty, and skip
> >tipc_node_xmit() for an empty chain. The empty chain would otherwise hit
> >tipc_lxc_xmit() -> buf_msg(skb_peek(list)), the same zero-skb case fixed for
> >tipc_link_xmit() in commit b77413446408 ("tipc: fix NULL deref in
> >tipc_link_xmit()").
>
> It needs to return earlier in tipc_named_node_up() like this:
>
> diff --git a/net/tipc/name_distr.c b/net/tipc/name_distr.c
> index ba4f4906e13b..60ccaa862162 100644
> --- a/net/tipc/name_distr.c
> +++ b/net/tipc/name_distr.c
> @@ -218,6 +218,10 @@ void tipc_named_node_up(struct net *net, u32 dnode, u16 capabilities)
>         spin_unlock_bh(&tn->nametbl_lock);
>
>         read_lock_bh(&nt->cluster_scope_lock);
> +       if (list_empty(&nt->cluster_scope)) {
> +               read_unlock_bh(&nt->cluster_scope_lock);
> +               return;
> +       }
>         named_distribute(net, &head, dnode, &nt->cluster_scope, seqno);
>         tipc_node_xmit(net, &head, dnode, 0);
>         read_unlock_bh(&nt->cluster_scope_lock);
>
> >
> >Fixes: cad2929dc432 ("tipc: update a binding service via broadcast")
> >Reported-by: Xiang Mei <xmei5@xxxxxxx>
> >Assisted-by: Claude:claude-opus-4-8
> >Signed-off-by: Weiming Shi <bestswngs@xxxxxxxxx>
> >---
> > net/tipc/name_distr.c | 8 ++++++--
> > 1 file changed, 6 insertions(+), 2 deletions(-)
> >
> >diff --git a/net/tipc/name_distr.c b/net/tipc/name_distr.c index
> >ba4f4906e13b..c04fea4650a5 100644
> >--- a/net/tipc/name_distr.c
> >+++ b/net/tipc/name_distr.c
> >@@ -192,7 +192,10 @@ static void named_distribute(struct net *net, struct
> >sk_buff_head *list,
> >               skb_trim(skb, INT_H_SIZE + (msg_dsz - msg_rem));
> >               __skb_queue_tail(list, skb);
> >       }
> >-      hdr = buf_msg(skb_peek_tail(list));
> >+      skb = skb_peek_tail(list);
> >+      if (!skb)
> >+              return;
> >+      hdr = buf_msg(skb);
> >       msg_set_last_bulk(hdr);
> >       msg_set_named_seqno(hdr, seqno);
> > }
> >@@ -219,7 +222,8 @@ void tipc_named_node_up(struct net *net, u32 dnode,
> >u16 capabilities)
> >
> >       read_lock_bh(&nt->cluster_scope_lock);
> >       named_distribute(net, &head, dnode, &nt->cluster_scope, seqno);
> >-      tipc_node_xmit(net, &head, dnode, 0);
> >+      if (!skb_queue_empty(&head))
> >+              tipc_node_xmit(net, &head, dnode, 0);
> >       read_unlock_bh(&nt->cluster_scope_lock);
> > }
> >
> >--
> >2.43.0
> >
>

Thanks for your review.  v2 sent.